The internal-combustion engines generally used today to power automobiles and trucks have a number of widely-recognized disadvantages. One problem with these engines is that many properties of the fuel they burn must fall within narrow limits for the engine to operate. For example, an automobile engine designed to run on gasoline with a high octane rating generally runs inefficiently or not at all if it is fueled with a low-octane gasoline. Natural petroleum must therefore be extensively processed in a refinery in order to produce gasolines and diesel fuels having the specific properties required to fuel automobile and truck engines.
A further drawback of internal combustion engines presently used to power transportation equipment is that the fuels they require must be highly volatile and are therefore a source of air pollution. Hydrocarbon vapors escaping into the atmosphere from these fuels constitute such a significant air pollution problem that new automobiles are generally required to have vapor recovery systems connected to their fuel tanks in order to reduce the amount of gasoline vapor which evaporates into the atmosphere. The problem of hydrocarbon vapors escaping into the atmosphere from the fuel systems of automobiles and trucks could be substantially eliminated if fuels of low volatility could be used. However, the use of such fuels has heretofore been considered impractical for automobile and truck engines.